PkmnLib.NET/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Moves/ForesightTests.cs

using PkmnLib.Dynamic.Libraries;
using PkmnLib.Dynamic.Models;
using PkmnLib.Dynamic.ScriptHandling;
using PkmnLib.Plugin.Gen7.Scripts.Moves;
using PkmnLib.Plugin.Gen7.Scripts.Pokemon;
using PkmnLib.Static;
using PkmnLib.Static.Libraries;
using PkmnLib.Static.Utils;

namespace PkmnLib.Plugin.Gen7.Tests.Scripts.Moves;

/// <summary>
/// Tests for the <see cref="Foresight"/> move script.
/// Behavior is verified against the Bulbapedia page for Foresight (Generation VII behavior: the
/// Generation II base effect with the Generation III, IV and V-to-VII changes applied).
/// The lasting part of the effect is implemented by the <see cref="ForesightEffect"/> volatile script,
/// which the move script is responsible for attaching to the target.
/// </summary>
public class ForesightTests
{
    /// <summary>
    /// Creates a fully mocked test setup for Foresight tests. The target is in battle, with a mocked
    /// battle library chain and the given evasion stat stage.
    /// </summary>
    private static (Foresight script, IExecutingMove move, IBattlePokemon target, IScriptSet volatileSet, IHitData
        hitData) CreateTestSetup(sbyte evasionStage = 0)
    {
        var script = new Foresight();
        var move = Substitute.For<IExecutingMove>();
        var target = Substitute.For<IBattlePokemon>();
        var hitData = Substitute.For<IHitData>();
        move.GetHitData(target, 0).Returns(hitData);

        var typeLibrary = Substitute.For<IReadOnlyTypeLibrary>();
        var staticLibrary = Substitute.For<IStaticLibrary>();
        staticLibrary.Types.Returns(typeLibrary);
        var library = Substitute.For<IDynamicLibrary>();
        library.StaticLibrary.Returns(staticLibrary);
        var battle = Substitute.For<IBattle>();
        battle.Library.Returns(library);
        target.Battle.Returns(battle);

        var volatileSet = Substitute.For<IScriptSet>();
        target.Volatile.Returns(volatileSet);
        target.StatBoost.Returns(new StatBoostStatisticSet
        {
            Evasion = evasionStage,
        });

        return (script, move, target, volatileSet, hitData);
    }

    /// <summary>
    /// Helper to extract all stat boost changes requested on the target through
    /// <see cref="IBattlePokemon.ChangeStatBoost"/>.
    /// </summary>
    private static IReadOnlyList<(Statistic stat, sbyte amount)> GetStatBoostChanges(IBattlePokemon target) =>
        target.ReceivedCalls().Where(c => c.GetMethodInfo().Name == "ChangeStatBoost")
            .Select(c => ((Statistic)c.GetArguments()[0]!, (sbyte)c.GetArguments()[1]!)).ToList();

    /// <summary>
    /// Bulbapedia: "Foresight also removes the Ghost type's immunity to Fighting and Normal moves for any
    /// moves used against the target. This effect remains until the target switches out".
    /// The lasting effect is implemented by attaching a <see cref="ForesightEffect"/> volatile script
    /// to the target.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetInBattle_AddsForesightEffectToTargetVolatile()
    {
        // Arrange
        var (script, move, target, volatileSet, _) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var addCall = volatileSet.ReceivedCalls().FirstOrDefault(c => c.GetMethodInfo().Name == "Add");
        await Assert.That(addCall).IsNotNull();
        await Assert.That(addCall!.GetArguments()[0] is ForesightEffect).IsTrue();
    }

    /// <summary>
    /// Bulbapedia (Generation III): "Foresight now causes all accuracy checks against the target to ignore
    /// any changes to the target's evasion stat stages."
    /// The engine models this by resetting a raised evasion stat stage back to zero (and preventing further
    /// changes through <see cref="ForesightEffect"/>).
    /// </summary>
    [Test, Arguments((sbyte)1, (sbyte)-1), Arguments((sbyte)3, (sbyte)-3), Arguments((sbyte)6, (sbyte)-6)]
    public async Task OnSecondaryEffect_PositiveEvasionStage_EvasionStageResetToZero(sbyte evasionStage,
        sbyte expectedChange)
    {
        // Arrange
        var (script, move, target, _, _) = CreateTestSetup(evasionStage);

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var changes = GetStatBoostChanges(target);
        await Assert.That(changes.Count).IsEqualTo(1);
        await Assert.That(changes[0].stat).IsEqualTo(Statistic.Evasion);
        await Assert.That(changes[0].amount).IsEqualTo(expectedChange);
    }

    /// <summary>
    /// Bulbapedia (Generation IV): "Foresight now only causes accuracy checks against the target to ignore
    /// changes to its evasion stat stages if its evasion stat stage is greater than 0."
    /// A lowered evasion stat stage therefore remains in effect: Foresight must not raise it back to zero.
    /// </summary>
    [Test, Arguments((sbyte)-1), Arguments((sbyte)-6)]
    public async Task OnSecondaryEffect_NegativeEvasionStage_EvasionNotRaised(sbyte evasionStage)
    {
        // Arrange
        var (script, move, target, _, _) = CreateTestSetup(evasionStage);

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert - a negative evasion stage may not be raised back towards zero
        var changes = GetStatBoostChanges(target);
        await Assert.That(changes.Any(c => c.stat == Statistic.Evasion && c.amount > 0)).IsFalse();
    }

    /// <summary>
    /// Bulbapedia (Generation III): "Foresight now causes all accuracy checks against the target to ignore
    /// any changes to the target's evasion stat stages."
    /// With an unchanged (zero) evasion stat stage there is nothing to reset, so no effective stat change
    /// may be requested.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_ZeroEvasionStage_NoEffectiveEvasionChange()
    {
        // Arrange
        var (script, move, target, _, _) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var changes = GetStatBoostChanges(target);
        await Assert.That(changes.Any(c => c.amount != 0)).IsFalse();
    }

    /// <summary>
    /// Bulbapedia (Generations V to VII): "Foresight will once again fail if used against a Pokémon already
    /// under its effect."
    /// When the target already has the <see cref="ForesightEffect"/> volatile script, the hit must fail.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetAlreadyUnderEffect_HitFails()
    {
        // Arrange
        var (script, move, target, volatileSet, hitData) = CreateTestSetup();
        volatileSet.Contains<ForesightEffect>().Returns(true);
        volatileSet.Contains(Arg.Any<StringKey>()).Returns(true);

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        await Assert.That(hitData.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Fail")).IsTrue();
    }

    /// <summary>
    /// Bulbapedia (Generation III): "Foresight now causes all accuracy checks against the target to ignore
    /// any changes to the target's evasion stat stages."
    /// For the evasion reset to actually take effect in a real battle, it must not be blocked by the move's
    /// own <see cref="ForesightEffect"/>: that script's <c>PreventStatBoostChange</c> hook prevents all
    /// evasion changes once attached. The reset must therefore either happen before the volatile script is
    /// added to the target, or be requested with <c>force: true</c>.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_PositiveEvasionStage_ResetNotBlockedByOwnEffect()
    {
        // Arrange
        var (script, move, target, volatileSet, _) = CreateTestSetup(2);
        var callOrder = new List<string>();
        volatileSet.Add(null!).ReturnsForAnyArgs(ci =>
        {
            callOrder.Add("Add");
            return (ScriptContainer?)null;
        });
        target.ChangeStatBoost(default, default, default, default).ReturnsForAnyArgs(ci =>
        {
            callOrder.Add(ci.ArgAt<bool>(3) ? "ChangeStatBoost:forced" : "ChangeStatBoost");
            return true;
        });

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert - the evasion reset must be able to take effect: either it happens before the
        // ForesightEffect volatile (which prevents evasion changes) is attached, or it is forced.
        var boostIndex = callOrder.FindIndex(c => c.StartsWith("ChangeStatBoost"));
        var addIndex = callOrder.IndexOf("Add");
        await Assert.That(boostIndex).IsNotEqualTo(-1);
        await Assert.That(addIndex).IsNotEqualTo(-1);
        await Assert.That(callOrder.Contains("ChangeStatBoost:forced") || boostIndex < addIndex).IsTrue();
    }
}